Electrostatic interactions between particles through heterogeneous fluid phases

Soft Matter ◽  
2017 ◽  
Vol 13 (37) ◽  
pp. 6647-6658 ◽  
Author(s):  
Dong Woo Kang ◽  
Mina Lee ◽  
Kyung Hak Kim ◽  
Ming Xia ◽  
Sang Hyuk Im ◽  
...  
Keyword(s):  
Electrostatic Interactions ◽  
Polymer Particles ◽  
Fluid Media ◽  
Electrostatic Repulsions ◽  
Fluid Phases

Gravitational confinement of polymer particles due to electrostatic repulsions between the particles through heterogeneous fluid media.

scholarly journals Encapsulation-free controlled release: Electrostatic adsorption eliminates the need for protein encapsulation in PLGA nanoparticles

2016 ◽  
Vol 2 (5) ◽  
pp. e1600519 ◽  
Author(s):  
Malgosia M. Pakulska ◽  
Irja Elliott Donaghue ◽  
Jaclyn M. Obermeyer ◽  
Anup Tuladhar ◽  
Christopher K. McLaughlin ◽  
...  
Keyword(s):  
Controlled Release ◽  
Electrostatic Interactions ◽  
Underlying Mechanism ◽  
Plga Nanoparticles ◽  
Protein Therapeutics ◽  
Polymer Particles ◽  
Protein Activity ◽  
Tunable Release ◽  
Effective Delivery ◽  
Therapeutic Molecules

Encapsulation of therapeutic molecules within polymer particles is a well-established method for achieving controlled release, yet challenges such as low loading, poor encapsulation efficiency, and loss of protein activity limit clinical translation. Despite this, the paradigm for the use of polymer particles in drug delivery has remained essentially unchanged for several decades. By taking advantage of the adsorption of protein therapeutics to poly(lactic-co-glycolic acid) (PLGA) nanoparticles, we demonstrate controlled release without encapsulation. In fact, we obtain identical, burst-free, extended-release profiles for three different protein therapeutics with and without encapsulation in PLGA nanoparticles embedded within a hydrogel. Using both positively and negatively charged proteins, we show that short-range electrostatic interactions between the proteins and the PLGA nanoparticles are the underlying mechanism for controlled release. Moreover, we demonstrate tunable release by modifying nanoparticle concentration, nanoparticle size, or environmental pH. These new insights obviate the need for encapsulation and offer promising, translatable strategies for a more effective delivery of therapeutic biomolecules.

A THEORETICAL COMPARISON OF CONFORMATIONAL FEATURES OF CALIX[4]AROMATICS

2004 ◽  
Vol 03 (01) ◽  
pp. 51-68 ◽  
Author(s):  
DI-FEI WANG ◽  
YUN-DONG WU
Keyword(s):  
Hydrogen Bonds ◽  
Electrostatic Interactions ◽  
Conformational Preference ◽  
Cone Conformation ◽  
Structural Modifications ◽  
Hydrogen Bonding Interactions ◽  
Partial Cone ◽  
Conformational Preferences ◽  
Intramolecular Hydrogen ◽  
Electrostatic Repulsions

Although there are tremendous studies about the conformational feature of calix[4]arenes and its analogies, no theoretical study has been done systematically about why some structural modifications could completely lead to a change of conformational preference. For example, calix[4]arene 1 adopts a cone conformation while its analogue calix[4]pyrrole 7 only adopts a 1,3-alternate conformation. So if this is only because of the effect of OH—OH hydrogen bonds, then why does O-methyl substituted calix[4]arene 2 still has cone conformation? In this paper, the conformational features of a series of seven calix[4]aromatics, calix[4]arene and calix[4]pyrrole related structures, have been investigated at BLYP/6–31G* level both in the gas phase and in CH 2 Cl 2 solution. The calculations demonstrated that three main factors influence the conformational preference of these calix[4]aromatics, i.e. the intramolecular hydrogen bond, the adjacent ring-ring electrostatic interaction and the intrinsic flexibility of the [14] metacyclophane framework. Calix[4]benzene 3 and calix[4]pyridine 4 have little conformational preferences due to their flexible [14] metacyclophane framework, the lack of hydrogen-bonding interactions and weak ring-ring electrostatic interactions. In contrast, calix[4]aromatics 1 and 5–7 have either intramolecular hydrogen bonds (1) or ring-ring electrostatic interactions (5–7). Consequently, calix[4]arene 1 has the cone preference and calix[4]pyrrole, calix[4]furan, and calixthiophene (5–7) have the 1,3-alternate preference. Methoxy calix[4]arene prefers a cone or partial cone conformation, because the 1,3-alternate and 1,2-alternate conformations are destabilized by electrostatic repulsions involving the methoxy group and the adjacent phenyl ring.

Immobilization of Acetobacter aceti by adhesion

1988 ◽  
Vol 34 (5) ◽  
pp. 638-644 ◽  
Author(s):  
M. P. Hermesse ◽  
C. Dereppe ◽  
Y. Bartholome ◽  
P. G. Rouxhet
Keyword(s):  
Electrostatic Interactions ◽  
Ferric Ions ◽  
Binding Agent ◽  
Acetobacter Aceti ◽  
Lower Cell Density ◽  
A Cell ◽  
Previously Treated ◽  
Electrostatic Repulsions ◽  
Hydrophobic Bonding ◽  
Reduced Surface

The attachment of three strains of Acetobacter aceti (ATCC 23747, ATCC 23748, NCIB 8246), with or without capsule, cultured under different conditions has been investigated in solutions of controlled pH. Various materials (silicates, organic polymers) have been used as supports, and the results have been related to the surface properties of the cells and supports. Cells that do not have a capsule do not adhere to the tested materials, whatever their hydrophobicity, unless the latter are previously treated by ferric ions to make their surface less negative. Cells that possess a capsule adhere to non-treated supports. In all cases the highest density of the adhering cellular film is obtained when the electrostatic repulsions between a cell and the support and between cells are reduced (surface charge of the support less negative, lower pH). The capsule influences adhesion by affecting the interplay between electrostatic interactions and hydrophobic bonding; moreover, capsule polymers may favor adhesion by acting as binding agent. The occurrence of cell flocculation gives rise to greater heterogeneity and lower cell density in the film of adhering cells.

Template mediated crystal engineering

1994 ◽  
Vol 52 ◽  
pp. 480-481
Author(s):  
Brigid R. Heywood ◽  
S. Champ
Keyword(s):  
Crystal Engineering ◽  
Electrostatic Interactions ◽  
Alkyl Chain ◽  
Crystallographic Axis ◽  
Two Dimensional ◽  
Engineering Process ◽  
Solution Interface ◽  
Extensive Program ◽  
Geometric Homology ◽  
Long Alkyl Chain

Recent work on the crystallisation of inorganic crystals under compressed monomolecular surfactant films has shown that two dimensional templates can be used to promote the oriented nucleation of solids. When a suitable long alkyl chain surfactant is cast on the crystallisation media a monodispersied population of crystals forms exclusively at the monolayer/solution interface. Each crystal is aligned with a specific crystallographic axis perpendicular to the plane of the monolayer suggesting that nucleation is facilitated by recognition events between the nascent inorganic solid and the organic template.For example, monolayers of the long alkyl chain surfactant, stearic acid will promote the oriented nucleation of the calcium carbonate polymorph, calcite, on the (100) face, whereas compressed monolayers of n-eicosyl sulphate will induce calcite nucleation on the (001) face, (Figure 1 & 2). An extensive program of research has confirmed the general principle that molecular recognition events at the interface (including electrostatic interactions, geometric homology, stereochemical complementarity) can be used to promote the crystal engineering process.

Characteristics of the Interaction between Thrombin Exosite1 and the Sequence 269-297 of Platelet Glycoprotein Ibα

1998 ◽  
Vol 80 (08) ◽  
pp. 310-315 ◽  
Author(s):  
Marie-Christine Bouton ◽  
Christophe Thurieau ◽  
Marie-Claude Guillin ◽  
Martine Jandrot-Perrus
Keyword(s):  
Platelet Activation ◽  
Electrostatic Interactions ◽  
Platelet Glycoprotein ◽  
Thrombin Receptor ◽  
Central Position ◽  
Amidolytic Activity ◽  
N Terminus ◽  
Hydrolysis Of ◽  
Chemical Cross Linking ◽  
Positively Charged

SummaryThe interaction between GPIb and thrombin promotes platelet activation elicited via the hydrolysis of the thrombin receptor and involves structures located on the segment 238-290 within the N-terminal domain of GPIbα and the positively charged exosite 1 on thrombin. We have investigated the ability of peptides derived from the 269-287 sequence of GPIbα to interact with thrombin. Three peptides were synthesized, including Ibα 269-287 and two scrambled peptides R1 and R2 which are comparable to Ibα 269-287 with regards to their content and distribution of anionic residues. However, R2 differs from both Ibα 269-287 and R1 by the shifting of one proline from a central position to the N-terminus. By chemical cross-linking, we observed the formation of a complex between 125I-Ibα 269-287 and α-thrombin that was inhibited by hirudin, the C-terminal peptide of hirudin, sodium pyrophosphate but not by heparin. The complex did not form when γ-thrombin was substituted for α-thrombin. Ibα 269-287 produced only slight changes in thrombin amidolytic activity and inhibited thrombin binding to fibrin. R1 and R2 also formed complexes with α-thrombin, modified slightly its catalytic activity and inhibited its binding to fibrin. Peptides Ibα 269-287 and R1 inhibited platelet aggregation and secretion induced by low thrombin concentrations whereas R2 was without effect. Our results indicate that Ibα 269-287 interacts with thrombin exosite 1 via mainly electrostatic interactions, which explains why the scrambled peptides also interact with exosite 1. Nevertheless, the lack of effect of R2 on thrombin-induced platelet activation suggests that proline 280 is important for thrombin interaction with GPIb.

Numerical Simulation on Dynamics and Thermal Decomposition of Spallation Polymer Particles Flying in Polymer Ablated Arcs

2015 ◽  
Vol 135 (11) ◽  
pp. 681-687 ◽  
Author(s):  
Takuya Nakagawa ◽  
Tomoyuki Nakano ◽  
Yasunori Tanaka ◽  
Yoshihiko Uesugi ◽  
Tatsuo Ishijima
Keyword(s):  
Numerical Simulation ◽  
Thermal Decomposition ◽  
Polymer Particles

Intrinsic Stacking Interactions of Natural and Artificial Nucleobases

2019 ◽  
Author(s):  
Drew P. Harding ◽  
Laura J. Kingsley ◽  
Glen Spraggon ◽  
Steven Wheeler
Keyword(s):  
Gas Phase ◽  
Electrostatic Interactions ◽  
Density Functional ◽  
Molecular Descriptors ◽  
Stacking Interactions ◽  
Interaction Energies ◽  
Functional Theory ◽  
Binding Partner ◽  
Heavy Atoms ◽  
Wide Range

The intrinsic (gas-phase) stacking energies of natural and artificial nucleobases were explored using density functional theory (DFT) and correlated ab initio methods. Ranking the stacking strength of natural nucleobase dimers revealed a preference in binding partner similar to that seen from experiments, namely G > C > A > T > U. Decomposition of these interaction energies using symmetry-adapted perturbation theory (SAPT) showed that these dispersion dominated interactions are modulated by electrostatics. Artificial nucleobases showed a similar stacking preference for natural nucleobases and were also modulated by electrostatic interactions. A robust predictive multivariate model was developed that quantitively predicts the maximum stacking interaction between natural and a wide range of artificial nucleobases using molecular descriptors based on computed electrostatic potentials (ESPs) and the number of heavy atoms. This model should find utility in designing artificial nucleobase analogs that exhibit stacking interactions comparable to those of natural nucleobases. Further analysis of the descriptors in this model unveil the origin of superior stacking abilities of certain nucleobases, including cytosine and guanine.

Solubilization of Itraconazole by Surfactants and Phospholipid-Surfactant Mixtures: Interplay of Amphiphile Structure, pH and Electrostatic Interactions

2020 ◽  
Author(s):  
Zahari Vinarov ◽  
Gabriela Gancheva ◽  
Nikola Burdzhiev ◽  
Slavka S. Tcholakova
Keyword(s):  
Nmr Spectroscopy ◽  
Electrostatic Interactions ◽  
Triazole Ring ◽  
Water Soluble ◽  
Single Chain ◽  
Surfactant Mixtures ◽  
Solubilization Capacity ◽  
Water Soluble Drugs ◽  
Hydrophobic Chain ◽  
Brick Dust

Although surfactants are frequently used in enabling formulations of poorly water-soluble drugs, the link between their structure and drug solubilization capacity is still unclear. We studied the solubilization of the “brick-dust” molecule itraconazole by 16 surfactants and 3 phospholipid:surfactant mixtures. NMR spectroscopy was used to study in more details the drug-surfactant interactions. Very high solubility of itraconazole (up to 3.6 g/L) was measured in anionic surfactant micelles at pH = 3, due to electrostatic attraction between the oppositely charged (at this pH) drug and surfactant molecules. <sup>1</sup>H NMR spectroscopy showed that itraconazole is ionized at two sites (2+ charge) at these conditions: in the phenoxy-linked piperazine nitrogen and in the dioxolane-linked triazole ring. The increase of amphiphile hydrophobic chain length had a markedly different effect, depending on the amphiphile type: the solubilization capacity of single-chain surfactants increased, whereas a decrease was observed for double-chained surfactants (phosphatidylglycerols). The excellent correlation between the chain melting temperatures of phosphatidylglycerols and itraconazole solubilization illustrated the importance of hydrophobic chain mobility. This study provides rules for selection of itraconazole solubilizers among classical single-chain surfactants and phospholipids. The basic physics underpinning the described effects suggests that these rules should be transferrable to other “brick-dust” molecules.

Hydration Free Energies of Organic Molecules in the FreeSolv Database Calculated with Polarized Atom In Molecules Atomic Charges and the GAFF Force Field.

2018 ◽  
Author(s):  
Maximiliano Riquelme ◽  
Alejandro Lara ◽  
David L. Mobley ◽  
Toon Vestraelen ◽  
Adelio R Matamala ◽  
...  
Keyword(s):  
Force Field ◽  
Functional Groups ◽  
Electrostatic Interactions ◽  
Organic Molecules ◽  
Force Fields ◽  
Chemical Elements ◽  
Atomic Charges ◽  
Free Energies ◽  
Molecular Systems ◽  
Solvent Model

<div>Computer simulations of bio-molecular systems often use force fields, which are combinations of simple empirical atom-based functions to describe the molecular interactions. Even though polarizable force fields give a more detailed description of intermolecular interactions, nonpolarizable force fields, developed several decades ago, are often still preferred because of their reduced computation cost. Electrostatic interactions play a major role in bio-molecular systems and are therein described by atomic point charges.</div><div>In this work, we address the performance of different atomic charges to reproduce experimental hydration free energies in the FreeSolv database in combination with the GAFF force field. Atomic charges were calculated by two atoms-in-molecules approaches, Hirshfeld-I and Minimal Basis Iterative Stockholder (MBIS). To account for polarization effects, the charges were derived from the solute's electron density computed with an implicit solvent model and the energy required to polarize the solute was added to the free energy cycle. The calculated hydration free energies were analyzed with an error model, revealing systematic errors associated with specific functional groups or chemical elements. The best agreement with the experimental data is observed for the MBIS atomic charge method, including the solvent polarization, with a root mean square error of 2.0 kcal mol<sup>-1</sup> for the 613 organic molecules studied. The largest deviation was observed for phosphor-containing molecules and the molecules with amide, ester and amine functional groups.</div>

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